Fuel-air induction system for carburetors



Aug. 15, 1961 e. E. SELDON FUEL-AIR INDUCTION SYSTEM FOR CARBURETORS Filed Oct. 6, 1958 F/& 3.

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2,996,289 FUEL-Am INDUCTION SYSTEM FOR CARBURETORS George E. Seldon, 534 N. Holmes Ave., Kirkwood, M0. Filed Oct. 6, 1958, Ser. No. 765,614 13 Claims. (Cl. 261--76) This invention deals with the problem of providing apparatus to mix air and fuel in correct proportions in a carburetor with a reservoir, especially the pan or mobile type of reservoir. Because of the difliculty of plumbing the moving pan to the stationary venturi, the tube or colunm for removing the mixed air fuel fluid is brought in over the reservoir wall and through the opening in the top. Hills, uneven ground, sloshing, relative accelerations such as braking, cornering, and pure acceleration, demand a high wall to be placed at the rim of the opening in the top of these reservoirs to prevent spilling. Because of this required height and the inability of the venturi to produce sufficient force to lift high density liquid fuel over this wall it becomes necessary to reduce the density of the material passing out of the removing tube. My application #716,720 is a parent application to this one and shows a similar pan type reservoir and metering tube. But it does not show a plan view of the metering tube at the center of the pan as this application does. The central location can however be inferred from the views given. This central location provides constant fuel head at the metering tube in adverse conditions.

It is an object then of this invention to provide a fuelair mixing column to allow low venturi pressure differentials to pick up fuel in the form of an emulsion and deliver it to the venturi.

It is also an object to provide a mixing column that will permit exceedingly low venturi pressure dififerentials to pick up and deliver sutficient fuel to provide a combustible mix when added to the main stream of aspirated air.

It is also an object of this invention to provide orificing of simple contour that can easily be made by drilling, yet provide combustible mixtures over the usable range of engine r.p.m.

It is an object of this invention to provide a liquid fuel pick-up that is concentric to the area of the fuel surface to minimize the effect of sloshing, accelerations and angular fuel surface in the reservoir, on steady flow of fuel-air mixture through the carburetor.

It is an object of this invention to provide a novel device for proportioning and mixing air and fuel in a predetermined ratio over a wide range of mixture flow rates.

FIGURE 1 is a plan view of section BB on FIGURE 2. It shows the path of the rich mixture through part of the auxiliary air circuit into the openings in the venturi.

FIGURE 2 is the elevation view of a section AA of FIGURE 1. It shows a venturi with its throat and the auxilary air circuit with its controlling orifices and a view through the pan type reservoir with its trunnions.

FIGURE 3 is an elevation view of a section C-C of FIGURE 2. It shows the mobile reservoir and the method of actuating the inlet valve and also parts of the metering column.

In FIGURES l and 2, 1 is a base on which the venturi 2 with its throat 3 is cast. The air is admitted to the throat through skirts 4 of the air horn 5. The skirts 4 are continued downward to meet the diffuser 6 (the expanding skirt part of the venturi). The continuation forms wall 7 enclosing an annular space 8 between it and the venturi throats 3. This annular space 8 provides a path through which the super rich fuel-air mixtures flow, to orifices 9 and the throats 3. A butterfly choke valve 2,996,289 Patented Aug. 15, 1961 10 is mounted on shaft 11 permitting the main air inlet passage 12 to be restricted. Most of the air aspirated into the carburetor flows through the main air passage 12 which consists of the skirts 4, the throats 3, the diffuser 6 of the venturi 2, the throttle barrel 13 and the intake manifold 14. A throttle 15 mounted on a shaft 16 controls the main fluid mixture flow through the carburetor.

The throat 6 is the point of highest air velocity hence the lowest static pressure. The difference between ambient and static pressure is called the venturi depression in this application. The super rich or high quality fuel-air mixture flowing in the auxiliary air system meets the main stream of incoming air at throat 6. It was admitted through the auxiliary fluid system comprising the orifices 9 and the space annulus 8 which is fed through mixture passage 17 formed by the walls 18. A long orifice 19 formed by its walls 20 feeds the air-fuel mixture into the passage 17. A removable plug 36 permits drilling orifice 19. This orifice 19 is calibrated in actual use. It is drilled or bored to a definite diameter determined from tests to control the total flow of air-fuel mixture in the auxiliary air system. The walls 20 and the skirt 21 together form a metering column 22 which determines the quality (the ratio of fuel to air) of the rich mixture of fuel and air flowing in the auxiliary system. An air orifice 23 admits air into the metering column 22. It is spaced y distance above the fuel surface 24. This distance y is calibrated to give optimum results.

The orifice 23 admits air only to the metering column. It is sized to control the quantity of air flowing for any given pressure differential. This sizing or calibrating is done after the instrument has been experimentally run and the best diameter determined for a specific engine by test or other means. A space 25 exists about the orifice 23 for the fuel and air to mix before entering the total mixture control orifice 19. This space 25 is known as a mixing chamber and is bounded on the bottom by fuel drawn up into the bore of the column in response to the venturi depression sensed by the auxiliary tube system through orifices 9. The walls or skirt 21 of the column form the vertical wall and the orifice with its flange define the upper boundary of the mixing chamber 25. Fuel 26 enters the column at the bottom of the skirt 21, through the opening 27 which as shown has substantially the same diameter as the bore above the skirt. There is no orifice or other means to restrict the flow of fuel into the column.

The fuel is contained in a pan type reservoir 28 which has trunnions 29 seated in bearings 30. The center-line through the trunnions and bearings forms a common axis, a straight line. This axis passes through or very close to the center of gravity of the reservoir and its contents the predetermined quantity of fuel. The reservoir is completely self-contained and adequate for the loads imposed upon it. The outboard bearing is carried by arm 39. As the fuel flows out through orifice 19 it is replaced by incoming fuel flowing past valve 31 which.

straddles seat 32 in inlet fitting 33 which connects into inlet boss 34 shown with a pipe tap 35. A skirt 36 attached to the reservoir 28 encircles inlet fitting 33 and the metering column 2.2. The skirt is high enough so that accelerating forces equivalent to 16 feet per second cannot spill fuel over the top.

Method 0 operation As the engine 37 aspirates the fuel-air mixture through the manifold 14, the auxiliary air system supplies a super rich mixture of fuel and air which it injects into the main air stream as the main air passes the throat 3 of the venturi. The super rich mixture enters through orifices 9. The main or primary air up to this point has no fuel in it. But as this main or primary air passes this throat plane, the super rich mix is injected into it and mixes with it to form a combustible mixture of fuel and The quality of this final mix is from 8 to 12% of the air by Weight, depending on r.p.m. of the engine. It is richer at low and high r.p.m. than at the middle rpm. range by usual practice.

The super rich mixture flows to the orifices 9 through passage 17 which in turn is fed by orifice 19. This orifice as stated controls the total flow rate of the super rich fuel-air mixture in the auxiliary air system. This orifice diameter is calibrated for a specific engine. The area may be experimentally or mathematically determined. Once the area is established it is expedient not to molest it. A plug 38 is provided to permit drilling, etc. Thercalibrated orifice leads into a mixing plenum chamber 25 which is substantially the same inside diameter as the skirt 21.

The engine aspirates air through the throat of the venturi. The higher the engine r.p.n1. and the greater the throttle opening the more air goes through the venturi throat. So venturi air speed is a function of the engine r.p.rn. and throttle opening. This air speed at the throat is obtained at the expense of static pressure in accordance with the well known Bernouli law total pressure drop, as long as the air flow can be conwhere q=lbs. per square foot. C=density in slugs per cubic foot or lbs. x 32.2 per cubic foot and V=velocity in feet per second. In the main air passage this pressure drop takes place at one place, the throat. But in the auxiliary system the pressure drop is divided into three steps at orifices 9, 19 and 23, and each is proportional to the other and the total pressure drop, as long as the air flow can be considered incompressible. The mass air flow through the main passage may well reach the transonic range. However, by proper proportioning it is quite possible to keep the flow in the auxiliary system in the incompressible range or at least near enough for no appreciable error. The pressure drop between the ambient pressure and the throat is the same whether it is considered from the opening 12 to the throat 3 or from outside the orifice 23 to the throat 3 through the auxiliary system. The pressure drop across the orifice 23 is. what remains after the drop across orifices 9 and 19, of

the total pressure drop, from 12 to 3. It is significantly less if the orifice 19 is relatively small and accounts for a large percentage of the total available pressure drop.

However, in this auxiliary system pressure drop across the orifice 23 is small at low engine r.p.m. It is always proportional to the total and the proportion is controllable by manipulating the area of it and the other orifices. The total pressure drop or venturi depression may run as high as p.s.i.g.

Whatever the amount of total depression, the drop at orifice 23 is less than the total in terms of inches of fuel, let us say, assume it at 1" of fuel. Hence fuel would rise in the column 21, 1", were it not for the air flowing through the orifice 23. But orifice 23 does admit air, and the lower rim of the orifice 23 is say Va" above the surface of the fuel. Now the air and fuel meet in the mixing space 25 and having rapid motion, mix violently, while the resulting rich mixture becomes an emulsion. This emulsion is much richer than a combustible mixture. In fact if 2% of the total air flows through the auxiliary system, it must here pick up all the fuel that finally is required by all of the air. That is the rich mix would be l00-:-2=5O times richer than the final combustible mixture. The density of the rich mixture is however much. less than liquid alone and it is easily lifted over the skirt 36.

The distance y is the distance that the solid fuel is lifted. Withlow engine r.p.m. there could be an air flow too small to produce sufficient differential pressure across orifice 23 to lift the fuel this distance (.125"). Which means the shorter y is made, the lower the air flow through the throat can be and produce a combustible mixture. Increasing y makes the rnixture leaner and decreasing it makes the mixture richer.

This disclosure teaches the correlation of series orifices 9 and 19 with the orifice 23 distance y above the fuel surface, to produce a combustible mixture of fuel and air in the main passage 12 over a range of engine r.p.rn.s.

I claim:

1. In a vehicular carburetor having a venturi with a throat; a reservoir for containing fuel; a fuel inlet tube to the reservoir with a control valve and means operating the control valve to maintain the constant liquid level in the reservoir; between said throat and said fuel level in the reservoir, a fuel outlet tube having a calibrated orifice for controlling therethrough the flow rate of a mixture of fuel and air, a connecting tube between said calibrated controlling orifice and said fuel exending into the reservoir to below the fuel level aforesaid and communicating into the reservoir to enable liquid to rise therein, means comprising, a second calibrated orifice through the wall of said connecting tube just above the surface of said fuel connecting to a point of air pressure higher than the venturi pressure to admit air at said higher pressure into said connecting tube, the arrangement of the second orifice above the liquid level when the carburetor is inactive providing that, at the start of operation of the carburetor air may be drawn into the connecting tube above the liquid therein, and both air and fuel may meet and mix in said connecting tube and be fed to said calibrated mixture flow rate controlling orifice and whereby said second calibrated air controlling orifice controls the ratio of air to fuel in the mixture of air and fuel passing through said calibrated orifice for controlling mixture flow to said throat.

2. In an operable vehicular carburetor; a main air induction tube having a venturi with a throat; a constant level mechanism with a fuel reservoir and a definite quantity of fuel therein; controllable means to admit fuel into said reservoir to establish a predetermined liquid level therein; connected between said throat and extending at least to below the aforesaid level of said fuel in said reservoir, a second induction tube having a long longitudinally bored metering column to' mix fuel and air and remove fuel from said reservoir and deliver it to said throat; in said column at a distance above the aforesaid level of the fuel surface a calibrated orifice to control the flow rate of fuel-air mixture therethrough, adjacent to and just above the aforesaid liquid level and between said mixture orifice and the said liquid level of the fuel a second.

calibrated orifice in the wall of said metering column, the orifice being connected to a source of air at atmospheric pressure for admitting air at atmospheric pressure, into said column, said bored column extending past the surface and into said fuel with no change in bore diameter between said second calibrated orifice and the fuel entry opening at the end of the column offering substantially an unrestricted passage for fuel to said second calibrated orifice Where air and fuel meet and mix just before passing through said calibrated mixture orifice in said column of said second induction tube.

3. In a vehicular carburetor having a venturi with a throat; a constant level mechanism with a reservoir for containing fuel, a fuel inlet tube with a control valve to establish a predetermined liquid fuel level in the reservoir; between said throat and said level, a fuel outlet tube having a calibrated fuel-air mixture quantity controlling orifice, a connecting tube between said calibrated controlling orifice and said fuel level, means for connecting the interior of the tube to a source of air at pressure above venturi. pressure comprising, a second calibrated orifice through the wall of said tube to admit air into said connecting tube, the second orifice being above the aforesaid fuel level in the reservoir, whereby both air and fuel meet and mix in said tube, and are fed to said calibrated controlling orifice and said second calibrated air orifice controls the ratio of air to fuel in the mixture of air and fuel passing through said calibrated controlling orifice to said throat.

4. In a vehicular carburetor; an air induction tube with a venturi having a throat; a reservoir for storing fuel, controllable means to establish a predetermined level of fuel in said reservoir; a secondary induction tube to carry a mixture of air and fuel from said reservoir to said throat, said tube including a hollow metering column with a longitudinal bore therethrough, extending into said reservoir above and below the said fuel level to enable the fuel level to be established therein, said column being vertical and substantially at right angles to the fuel level at normal horizontal altitudes of the carburetor, means for connecting the interior of the column to a source of air at pressure above venturi pressure, comprising a calibrated air orifice in the side of the column above the aforesaid level of the fuel to admit air into said bore, the bore extending downwardly into said fuel and being sized to present substantially no further restriction to the flow of fuel therethrough and said fuel and said air being violently mixed at the point of mutual contact; and the secondary induction tube having also a calibrated orifice connecting with the hollow metering column and with the throat, to control the flow of the air fuel mixture between said calibrated air orifice and the point in said secondary tube at which the mixture is delivered to said throat, and said calibrated air orifice being the sole opening for admitting air into said secondary in duction tube.

5. In an operable vehicular carburetor; a main air induction tube having a venturi with a throat; a constant level mechanism with a fuel reservoir the level mechanism being adapted to provide a predetermined fuel level in the reservoir; an auxiliary fuel-air induction tube having three openings, one of said openings being the outlet, hermetically sealed into the throat of said venturi; said tube at its inlet end including a metering column standing substantially vertical with its lower extremity including the second extending into the reservoir with a bottom opening well submerged below the said level for fuel in said reservoir, said bottom opening being the second of said openings, said column being axially bored throughout its length in two diameters in tandem, the upperof said bores being the smaller and being a calibrated orifice for controlling the flow rate of fuel-air mixture through the auxiliary tube, means connecting a source of air at greater than venturi pressures into the said large diameter bore of said column including a second calibrated orifice for admitting said air into said column, said orifice being the third opening into said auxiliary tube and said orifice being a predetermined distance above the said fuel surface, whereby the fuel and air entering said column mix in the large diameter bore of said column; said mixture becoming the rich mixture, which mixture on being added to the air at the throat of the venturi produces a combustible fuel-air mixture.

6. In a carburetor for a fuel-air engine; an air duct with a venturi having a throat where a venturi pressure depression occurs on passage of primary air therethrough, by the aspiration of air by said engine; a fuel reservoir adapted to contain a predetermined quantity of fuel e tablishing the surface level at a predetermined elevation; a tube connecting said fuel to said throat to convey primary fuel from said reservoir to said throat, said primary fuel to meet and mix with said primary air to provide a combustible mixture of fuel and air for said engine; at the fuel inlet end of said tube a metering column which pierces said fuel surface to be immersed in fuel, whereby the exterior of said column may be surrounded by air above said surface, and by fuel below said surface; a fuelair mixing chamber within said column extending above and below said fuel surface, said mixing chamber having a calibrated orifice as the outlet into the column, a calibrated orifice through the wall of the column above the surface of the fuel to admit air to said mixing chamber and an opening below the surface of the fuel to admit fuel into said chamber, said opening permitting substantially unrestricted fuel flow into said mixing chamber.

7. In a vehicular carburetor; a main air duct including a venturi with a throat, a tube with a control valve for admitting fuel, a self-contained reservoir for receiving and storing fuel to a predetermined level determined by the control valve, trunnions on a common axis on said reservoir, the axis of said trunnions substantially passing through the center of gravity of said reservoir and the fuel therein, means whereby motion of said reservoir about said trunnions actuates said control valve, a tube extending from said throat to said fuel level in said reservoir for delivering fuel to said throat of said venturi, said fuel removing tube extending to the fuel level for entering said fuel in a direction such that the centerline of said tube substantially passes through the center of gravity of the reservoir with its fuel contents and the axis of said trunnions.

8. In a vehicular carburetor; a venturi having a throat for admitting air; a tube with a control valve to admit fuel; a self-contained reservoir to store a quantity of fuel to a predetermined level determined by the control valve; said reservoir having trunnions on a common axis about which said reservoir has limited rotative freedom with respect to said venturi and said inlet tube, means whereby said valve is actuated by said rotation of said reservoir about said axis to maintain said predetermined quantity of fuel in said reservoir; a tube to remove fuel from said reservoir and deliver it to said throat in said venturi; at the inlet end of said fuel removing tube the centerline of said tube passing substantially through the axis of said trunnions about which said reservoir turns.

9. In a carburetor with a self-contained mobile reservoir for receiving and storing a quantity of fuel; a venturi; means to remove fuel from said reservoir'and deliver it to said venturi; means to add sufficient fuel to said reservoir to constantly maintain a predetermined quantity of fuel in said reservoir with a free surface and an air space thereabove; said fuel removing means including a metering column having an air inlet port at the side of said column above said free surface and a nonrestricting fuel inlet port below said free surface, said column being disposed to pierce said free upper surface perpendicularly and the center-line of said column substantially passing through the center of gravity of said reservoir and the fuel contents.

10. In a carburetor, a venturi, a fuel reservoir, means to establish a predetermined liquid level in the fuel reservoir and means to provide atmospheric pressure above the liquid level, means providing a mixing column over the reservoir and extending from above the liquid level in the reservoir to below it, and in communication with the fuel reservoir below the liquid level so as to receive fuel therefrom and to establish a level corresponding to that in the fuel reservoir when the carburetor is inoperative; passage means from the mixing column above the liquid level to the venturi to conduct fuel from the mixing column into the venturi when the venturi is subjected to subatmospheric pressures; and means comprising an atmospheric air port connecting the mixing column above the aforesaid liquid level in the mixing column, to atmosphere, so that the subatmospheric pressures in the venturi can produce an air flow through said air port into the mixing column and via the passage means to the venturi, to entrain fuel therefrom and conduct an air-fuel mixture to the venturi.

11. The carburetor of claim 10, with the atmospheric air port being of a predetermined size to produce a pressure drop in air flowing through it, whereby atmospheric pressure on the fuel in the fuel reservoir can elevate fuel I r V in the mixing column with respect to the atmospheric the venturi and pivot means rockably suspending the bowl port. a on the fulcrum means to be rockable with respect to the 12. The carburetor of claim 10, wherein the passage inverted tube mixing column. means comprises a restrictive passage producing a predetermined pressure drop in the fluid mixture flowing 5 References Cited in the file of this patent through it.

13. The carburetor of claim 10, wherein the mixing UNITED STATES PATENTS column is an inverted tube fixed to the venturi, and the 2,621,911 Lindsteadt Dec. 16, 1952 fuel reservoir is a bowl having fulcrum means fixed to 2,757,914 Ball Aug. 7, 1955 

